Application of bi-linear log-log S-N model to strain-controlled fatigue data of aluminum alloys and its effect on life predictions

Bi-linear log-log model is applied to stress amplitude versus fatigue life data of 14 aluminum alloys. It is shown that the bi-linear S-N model provides a much better representation of the data than the commonly used linear model for Al alloys. The effects of bi-linear model on stress-strain, stress-life, and strain-life curves are discussed. Life predictions of aluminum alloys based on linear and bi-linear models are also compared and discussed. Estimations of the bi-linear fit constants from the linear fit constants are then presented.